Vastupidiseid

Vastupidiseid is an Estonian adjectival form derived from vastupidine, meaning opposite or reverse. It is the partitive plural form used to describe a group of things that are opposite to something else, as in vastupidiseid väiteid, meaning opposite/contrary claims.

The term is commonly used in written Estonian to refer to items, ideas, or concepts that are in opposition or contrast to another set. It functions as an adjective modifying a plural noun in the partitive case; the corresponding noun for “opposites” in noun form is typically vastandid (antonyms) rather than vastupidised, which is less standard as a standalone noun.

In practice, vastupidiseid appears across domains such as language, philosophy, and science. In philosophy and logic, it relates to contraries or opposing properties and propositions. In linguistics, it intersects with the study of antonyms and semantic oppositions. In mathematics or related sciences, the root concept is often expressed with terms like inverse or opposite, as in vastupidine funktsioon (inverse function) or vastupidine operatsioon (inverse operation), where one action undoes another.

Usage notes: vastupidiseid is specifically a partitive plural form and is used when the noun it describes is in the partitive case. For example, vastupidiseid väiteid refers to a set of claims that are opposite or contrary to another set. While the word conveys opposition, Estonian also commonly uses vastandid or antonüümid as the standard nouns for “opposites.”